1. Field of the Invention
The present invention relates to a human-robot interactive system wherein a robot and a human simultaneously share a same work space to perform interactive work.
2. Description of the Related Art
In recent years, human-robot interactive systems have been developed in which humans and robots are stationed mixed together on the production floor and production work is divided and performed split between the humans and robots. Such human-robot interactive systems are expected to reduce running costs in production and to improve production efficiency.
However, in a human-robot interactive system, there are dangers such as a robot striking a human or fingers of a human being caught between the arms of a robot. In particular, when a robot can operate at a high speed or when the power of a robot is large, a human may receive excessive force from the robot. Therefore, safety measures against such dangers are sought for a human-robot interactive system.
A conventional robot system is provided with a collision detection function which detects collision of a robot with its surroundings based on abnormal torque generated at the manipulator part of the robot. If collision is detected by this collision detection function, control is performed to stop the operation of the robot or otherwise lighten the collision force. Due to this, the damage to the robot and the devices provided at the robot as well as surrounding equipment is kept to a minimum.
However, when using a collision detection function for detecting collision between a human and a robot, it is necessary to raise the sensitivity to collision in order to ensure safety of the human. For this reason, it is sought to precisely estimate the frictional torque of the gears or speed reducers etc. provided at the different parts of a robot. In this regard, the frictional torque fluctuates depending on the outside air temperature and the operating state of the robot, so estimating the frictional torque with a high precision is difficult. Therefore, it was difficult to precisely detect collision between a human and a robot from the torques of the manipulator part of a robot and prevent harm to the human.
Further, Japanese Patent No. 3099067, Japanese Patent No. 4168441, Japanese Patent Publication (A) No. 2008-213119, and Japanese Patent Publication (A) No. 2009-34755 disclose a conveyance robot which conveys an object. Such conveyance work is interactive work where a human and a robot pick up the two sides of a carried object when conveying a carried object with large dimensions or a heavy carried object. Further, the force sensor which is provided between the robot and the carried object detects the direction of the force which the human performing the interactive work applies and has the robot assist conveyance in that direction. The art which is disclosed in Japanese Patent No. 3099067, Japanese Patent No. 4168441, Japanese Patent Publication (A) No. 2008-213119, and Japanese Patent Publication (A) No. 2009-34755 detects the force generated through a carried object between a human and a robot and enables control of the robot so that the generated force does not exceed a predetermined value.
However when a human directly contacts a robot without a carried object interposed between them, the force which occurs between the human and the robot is not detected. Further, even if attaching a force sensor for detecting force between the arm and hand of a robot etc., it is not possible to detect contact of the human at the arm portion of the robot which the sensor cannot detect. For this reason, in the prior art, it was not possible to provide a robot system which enabled safe interactive work when there was a possibility of a human and a robot coming into direct contact.
The present invention was made in consideration of this problem and has as its object the provision of a human-robot interactive system which can ensure safety of a human even in an environment in which a human and a robot can contact each other.